Terrific acting and fight film cliches battle to a split decision in Antoine Fuqua’s “Southpaw,” further proof both of Jake Gyllenhaal’s awesome range and of the odds against making a truly original boxing picture.

Gyllenhaal is mesmerizing as Billy Hope, who has turned a tormented childhood on the streets into a lucrative career as the light heavyweight champion of the world.

Billy is not a subtle fighter. Fueled by anger, he absorbs punch after punch until his opponent is worn out, then murders the bum. This strategy usually leaves him with a championship belt and a face like a raw Big Mac.

In contrast to his rage in the ring, Billy’s home life is actually kind of normal. Yeah, he lives in a gated multimillion-dollar compound outside NYC, but his relationships with his wife, Maureen (Rachel McAdams), whom he has been with since his days in juvie, and their daughter, Leila (Oona Laurence), are practically blissful.

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But happy homes don’t make for dramatic movies. The screenplay by Kurt Sutter (creator of cable’s “Sons of Anarchy”) relies on over-the-top melodrama to remove McAdams’ Maureen from the scene, setting Billy on a downward spiral that will see him lose his boxing license, his title, his wealth and his mind.

Worst of all, he loses Leila to the child welfare folks.

Mostly “Southpaw” is about how — having been reduced to a lowly and primitive state — Billy slowly comes back. His Yoda in all this is Tick (Forest Whitaker), who used to train big-time boxers but now operates a rundown gym catering to at-risk kids.

Under Tick’s tutelage Billy learns to control his anger, employ defensive tactics (apparently for the first time) and develop the patience necessary both to win in the ring and earn the trust of a dubious family court judge.

Director Fuqua, who established his bona fides with 2001’s “Training Day” and has been trying to regain his mojo ever since, brings a gritty realism, employing handheld cameras and grungy settings (you can practically smell the mildew), concentrating on the pre-fight rituals and the spectacle of a championship bout.

The fight scenes are actually pretty terrific. They look unrehearsed — less choreography than spontaneous melee — and are bursting with power.

On the downside, whole chunks of “Southpaw” have been lifted from other films: “The Champ” (boxer-child love story), the “Rocky” franchise (an opponent, played by Miguel Gomez, who is less character than arrogant supervillain), “Raging Bull” (the way the camera artfully dwells on Billy’s bruised/defiant features), “The Fighter” (how family and friends can nurture or gnaw at a boxer).

Of course there is the obligatory training montage leading up to the final confrontation. And the overall tone is absolutely humorless.

Perhaps at this stage it’s impossible to make a fight movie that isn’t a recycling project.

Happily, the film has Gyllenhaal.

Oh, he gets solid support from McAdams (who transforms from girl next door to sexy veteran of the slums), Whitaker (always solid) and Laurence (whose owlish presence suggests one of those old souls in a young body).

But Gyllenhaal is the main attraction. This is an overwhelmingly physical performance. Billy is largely inarticulate, but the way he looks and moves — particularly the haunted eyes that dominate his face when Billy’s entire world implodes — speaks volumes.

Gyllenhaal reportedly spent five months training as a boxer, and it shows. He seems a natural in the ring, and his body has been sculpted until it’s an anthropomorphic coiled spring.

That is nicely balanced by the character’s humanity. Unlike the saintly Rocky Balboa, Billy Hope has plenty of not-so-admirable traits, but his love for his daughter always comes through.